Fastening means severable by ignition of an explosive charge

ABSTRACT

A threaded fastener having means for effecting a severing thereof at a predetermined location upon the electrical ignition of an explosive charge, wherein an explosive cartridge is disposed within the body of the threaded fastener to cause a shearing off of the fastener at the desired location without destroying the external threaded portion of the fastener.

United States Patent Gawlick et al. [45] Jul 11, 1972 [$4] FASTENINGMEANS SEVERABLE BY [56] References Cited IGNITION OF AN EXPL SIVE HAR 0C GE UNTTED STATES PATENTS [72] Inventors: Heinz Gawlick, Boenerstrasse32, Furth; 2 065 333 [2/1936 Kirley 85/39 fi sgg gg al 'f 2,556,6726/1951 Bergh et al.. ....89/l.5 F x y 2.8l5,698 [2/1957 Burrows..89/lt0l X [22] Filed: April 23, 1969 3,119,298 1/1964 Brown ..89/1 70]X 318,520 Primary Examiner-Samuel w. Engle Attorney-Craig, Antonelli &Hill [30] Foreign Application Priority Data [57} CT 1968 Germany 17 7]2l A threaded fastener having means for effecting a severing thereof ata predetemlined location upon the electrical igni- [52] us 0 "89/1 85mm,7:11 tion of an explosive charge, wherein an explosive cartridge is Cldisposed within the body of the threaded fastener to cause a [5|] nt...Fl6b 19/04 shearing of the fastener at the desired location wihou [58] Field Search I g/ l I'D/ destroy n e external threaded portion of thefastener.

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sum 2 OF 2 INVENTORS HEINZ GAWLICK HELLIUT BENDLER ATTORNEYS FIG."

FASTENING MEANS SEVERABLE BY IGNITION OF AN EXPLOSIVE CHARGE BACKGROUNDOF THE INVENTION The present invention pertains to a screw or rivet orother threaded fastener which can be severed at a predetermined locationby the electrical ignition of an explosive charge without destroying orseverely damaging the external threaded portion thereof.

Prior attempts to produce a threaded fastener which can be severed bymeans of an explosive charge have proved unsuccessful. One of theprimary disadvantages inherent within the attempts to provide such athreaded fastener has been the lack of reliability as to ensuring theshearing off of the threaded fastener at the desired location withoutexcessively damaging the external or threaded portion of the fastener.Additionally, the threaded fasteners having explosive cartridge meansincorporated therein in use heretofore have been so cumbersome as topreclude the construction of a fastener of this type with a relativelysmall shank diameter.

Accordingly, it is an object of the present invention to provide athreaded fastener incorporating an electrically ignitable explosivecharge for effectively shearing off the fastener at a predeterminedlocation upon the electrical ignition of the charge without excessivelydamaging the external threaded portion of the fastener.

Further, it is an object of the present invention to provide a fastenerof the type described above which, by virtue of the novel and ruggedconstruction thereof, facilitates the production of the fasteners withrelatively small dimensions.

Finally, it is an object of the present invention to provide a fastenerof the type described hereinabove which is relatively simple andinexpensive to produce and which is characterized by greater reliabilitythan those in use heretofore.

SUMMARY OF THE INVENTION The foregoing objects are accomplished, inaccordance with the present invention, by disposing within a screw orrivet body an explosive charge and an electrical detonator and arrangingthese, with respect to a joint formed at the location where shearing isintended, such that only that portion of the weakened joint is shearedoff upon ignition of the explosive charge, thus precluding excessivedamage of the remaining portion of the fastener. The detonator employedin connection with the fastener constructed in accordance with thepresent invention is a primer cap operating on the basis of the apertureprinciple or, alternatively, a bridge fuse. Because of the novel designand rugged construction of the relatively small primer, it is possibleto provide threaded fasteners of the type described above having a shankdiameter as small as 7mm.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects, features andadvantages of the present invention will become more readily apparentfrom the detailed description hereinbelow, when considered inconjunction with the accompanying drawings, wherein:

FIG. 1 represents a cross-sectional view of an explosive cartridge whichcan be employed in connection with the fastener constructed inaccordance with the present invention;

FIGS. 2 and 3 represent cross-sectional views through a modifiedcartridge adapted for incorporation within the fastener contemplated bythe present invention;

FIG. 4 represents a cross-sectional view through another type ofexplosive cartridge useful in conjunction with the present invention;

FIG. 5 represents a cross-section through a screw incorporating anexplosive cartridge;

FIG. 6 represents a cross-sectional view through a screw provided with abridge fuse-primed explosive cartridge;

F IG. 7 represents a cross-sectional view through a machine screwincorporating an explosive cartridge;

FIGS. 8 and 9 represent screws incorporating riveted joints adapted tobe sheared off by the explosive cartridge disposed within the screw;

FIG. 10 represents a cross-sectional view through a rivet incorporatingan explosive cartridge; and

FIG. 11 represents a cross-sectional view through a screw having apinned joint adapted to be sheared off by the explosion of the cartridgedisposed within the screw.

DETAILED DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 illustrate acartridge 1 including a conventional electrical primer cap 2 whichdetonate in accordance with the aperture principle; the primer cap 2includes an extended metal portion 3 and encloses a charge of explosivepowder 4. The pole piece 5 can be extended, as illustrated in FIG. 2,for making contact or, alternatively, it can serve, as illustrated inFIG. 3, as the lead wire. The various component parts are enclosedwithin cartridge case 6.

An alternative configuration of the explosive cartridge is representedin FIG. 4, wherein a conventional powder cartridge 7 is provided with anelectrical detonator 8. This embodiment is contemplated for fasteningelements of greater size which require a stronger explosive charge foreffective severing.

FIG. 5 illustrates a screw incorporating an explosive charge 4therewithin. In this connection, the otherwise conventional cartridgecase 6 is constructed in the form of a shank 9 and provided with a screwhead 10. Within the shank 9, the pole piece 5 is provided, insulatedwith respect to shank 9 by means of an insulating insert ll. Betweenpole piece 5 and spacer ring 12, an insulating disk 13 is interposed.Shank 9 is riveted, at 14, thus firmly pressing spacer ring 12 againstpole piece 5. After insertion of primer cap 2 and powder charge 4, thethreaded portion 15 of the screw is fastened within shank 9. Thefastening can be effected by threaded engagement, by metal cementing, byriveting, or other like methods.

In FIG. 6, an embodiment is illustrated incorporating a bridge fuse inplace of the aperture primer means illustrated in FIG. 5. The primerpellet 16 is embedded within a part 17 formed from a synthetic material.The powder 18 required for effecting separation of the screw is disposeddirectly above the primer pellet 16. The embodiment according to FIG. 6is simpler than that of FIG. 5, but does not exhibit the same strengthduring handling of the wire, because of the inherent instability of thebridge fuse utilized therein.

The strength of screws or rivets constructed in accordance with thepresent invention depends upon the type and design of the connection ofthe component parts thereof. FIG. 7 illustrates a normal machine screw.The threaded portion 15 is provided with an additional thread 19 forjoining the threaded portion 15 to the screw head 20 by means ofthreaded engagement after the cartridge 1 has been introduced therein.The cartridge 1 will, upon ignition, destroy the weaker thread 19 in theinterior of the screw, thus causing a separation of the screw head 20from the threaded portion 15.

In FIGS. 8 and 9, a riveting 21 is provided in place of the secondarythread 19 for securing the component parts of the screws. A wedge 22consisting of a stronger material effects, during compression, theriveting 21; for protection of the cartridge l, the wedge 22 rests upona steel ring 23. One embodiment of a rivet including an explosivecartridge therein is illustrated in FIG. 10.

In FIG. 11, the joint between the threaded portion 15 and the screw head20 is effected by means of a pin 24. The gas pressure produced duringignition of the explosive charge is effective to cause the pin 24 to besheared, thus effecting the separation of the threaded portion I5 fromthe screw head 20.

While the present invention has been described hereinabove withreference to but a few embodiments, it is to be understood that thescope of the invention is not limited to the specific details of theillustrated embodiments, but is susceptible of numerous changes andmodifications as would be apparent to one with normal skill in thepertinent technolo- What is claimed is:

l. A fastening device having means for causing separation thereof at apredetermined location, comprising: first and second portions, eachportion having external fastening means adapted to respectively engagetwo structures to be fastened together, said first portion defining aninternal chamber, explosive charge means disposed within said internalchamber and means for selectively detonating said explosive chargemeans, said first portion and said second portion having internaldetachable riveted connecting means, said connecting means adapted to bedestructively disconnected upon detonation of the explosive chargemeans, said connecting means forming a gas-tight seal about theexplosive charge means to preclude the premature escape of the explosionpressure gases upon detonation of the explosive charge means, saidconnecting means including wedge means disposed within the internalchamber of said first portion for cooperating with said rivetedconnecting means, further characterized in that protective means aredisposed in the internal chamber of said first portion to protect theexplosive charge during assembly of the device, said protective meansincluding rigid abutment means extending between said wedge means and apart of said first portion.

2. A device as in claim 1, further characterized in that said protectivemeans is a metal ring disposed about said explosive charge and inengagement with both said wedge means and with the end walls of theinternal chamber.

3. A device as in claim 1, further characterized in that said externalfastening means includes thread means and screw head means,respectively.

4. A device as in claim I, further characterized in that said externalfastening means includes rivet heads.

5. A device as in claim 1, further characterized in that said externalfastener means includes thread means on each of the two portions.

6. A device as in claim 1, further characterized in that said means forselectively detonating said explosive charge means includes electricalcontrol means.

l II I 1!

1. A fastening device having means for causing separation thereof at apredetermined location, comprising: first and second portions, eachportion having external fastening means adapted to respectively engagetwo structures to be fastened together, said first portion defining aninternal chamber, explosive charge means disposed within said internalchamber and means for selectively detonating said explosive chargemeans, said first portion and said second portion having internaldetachable riveted connecting means, said connecting means adapted to bedestructively disconnected upon detonation of the explosive chargemeans, said connecting means forming a gas-tight seal about theexplosive charge means to preclude the premature escape of the explosionpressure gases upon detonation of the explosive charge means, saidconnecting means including wedge means disposed within the internalchamber of said first portion for cooperating with said rivetedconnecting means, further characterized in that protective means aredisposed in the internal chamber of said first portion to protect theexplosive charge during assembly of the device, said protective meansincluding rigid abutment means extending between said wedge means and apart of said first portion.
 2. A device as in claim 1, furthercharacterized in that said protective means is a metal ring disposedabout said explosive charge and in engagement with both said wedge meansand with the end walls of the internal chamber.
 3. A device as in claim1, further characterized in that said external fastening means includesthread means and screw head means, respectively.
 4. A device as in claim1, further characterized in that said external fastening means includesrivet heads.
 5. A device as in claim 1, further characterized in thatsaid external fastener means includes thread means on each of the twoportions.
 6. A device as in claim 1, further characterized in that saidmeans for selectively detonating said explosive charge means includeselectrical control means.